What causes autism spectrum disorder (ASD)?

Nobody knows what causes autism. Some scientists believe there is a biological cause that affects the working of the brain, but this has not been proven. It is possible there are many factors that could interact with one another which could cause different characteristics in each individual with autism.

Parents do not cause autism. No factors in a child’s experiences or in parenting styles are responsible for autism.

Source: Center for Autism & Related Disabilities (CARD)

Doctors don't know what causes autism spectrum disorder (ASD), but they are working hard to find out. What they do know is that ASD often runs in families, so a person is more likely to have ASD if a close family member also has it.

The cause of autism is unknown. Current theories of what may cause autism include birth complications, infections, genetic factors and toxic exposures. The Centers for Disease Control and Prevention (CDC) has done significant studies that have successfully disproven the possibility of vaccines being the cause of autism.

About one in 110 children are diagnosed with autism, also known as Autism Spectrum Disorders or ASD, every year, according to the Centers for Disease Control and Prevention. Boys are four times as likely as girls to have autism. Researchers believe there may be many causes for the disease, including several genetic mutations.

Autism was first identified in 1943, but we still don't know what causes it. Since people are either born with autism or the potential to develop it, scientists are studying both genetic and environmental factors.

  • Genetic factors. Scans show differences in brain shape and structure in people with autism. Scientists think these changes are genetic.
  • Environmental factors. If a person has a genetic tendency toward autism, certain environmental factors may "trigger" it. Factors being studied include viral infections, metabolic imbalances and exposure to certain chemicals.
  • Not vaccines. There are no proven links between vaccines and autism. Research studies have repeatedly shown identical autism rates for patients who have received vaccines (such as the polio vaccine or mumps, measles and rubella [MMR]) or vaccine preservatives (such as thimerosal) and patients who have not received them.

About one in 166 children are affected by autism, and it occurs in boys 3 to 4 more times often than girls. However, this complex developmental disorder affects people to varying degrees. The cause is unknown, but genetic and environmental factors play a role. It is the result of abnormal development of certain parts of the brain.

From Good Kids, Bad Habits: The RealAge Guide to Raising Healthy Children by Jennifer Trachtenberg.


Good Kids, Bad Habits: The RealAge Guide to Raising Healthy Children

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There is very good data implicating genetics as the major cause of autism. The genetic changes identified to date show that there are many hundreds of genes that can contribute to autism. Mutations that increase risk for autism can be chromosomal abnormalities, small structural changes, or even single base changes. In some cases the genetic changes are de novo, which means the mutations occur in the egg or sperm.

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Scientists are not certain about what causes autism spectrum disorder (ASD), but it is likely that both genetics and environment play a role. Researchers have identified a number of genes associated with the disorder. Studies of people with ASD have found irregularities in several regions of the brain, including abnormal levels of serotonin or other neurotransmitters in the brain. These abnormalities suggest that ASD could result from the disruption of normal brain development early in fetal development. This could be caused by defects in genes that control brain growth and regulate how brain cells communicate with each other, possibly due to the influence of environmental factors on gene function. Although intriguing, these findings are preliminary and require further study. The theory that parental practices are responsible for ASD has long been disproved.

This answer is based on source information from the National Institute of Neurological Disorders and Stroke.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.